TWO-ELEMENT CONTROL SYSTEM FOR A LOAD-MOUNTED TOOL

Abstract

The control system for synchronizing the movements of two elements, for example a grapple (3) and a handling device (2) such as a bucket, includes a synchronization system (6) for the control systems (1, 4) which modifies the positions of the two elements (2, 3) simultaneously with a series hydraulic circuit. The elements have different position ranges, and the system includes a motion continuation system which ensures that, when one of the elements reaches a stop position, the other element continues its movement to a stop position. (See Figure 1 for abbreviations.)

Description

Description Title of the invention: TWO-WAY CONTROL SYSTEM ELEMENTS OF A TOOL CARRIED BY A LOADER FIELD OF THE INVENTION

[0001] — The present invention relates to a system for controlling two elements. These two elements can form a tool carried by a front loader. A system of control allows the two elements of said tool carried by the loader to be operated front of tractors used in agriculture or other vehicles used in the field of public construction works for example. TECHNOLOGICAL BACKGROUND

[0002] In the field of movement synchronization control systems of two elements, for example a claw and a handling device such as a bucket, the claw and the handling device constituting a tool carried by a loader, it means of synchronizing the operation of control means are known, so that, on the one hand, the movements of opening the claw and tipping of the handling organ are carried out concomitantly and that on the other hand the movements closing the claw and lifting the handling device are also carried out concomitantly.

[0003] Document FR2868794 is an example in which the movements of the two elements of the tool may be synchronized, i.e. performed at the same time.

[0004] — However, the synchronization control systems disclosed in the document FR2868794 does not allow the movement to continue when one of the elements, bucket or claw, has reached the stop. The range of movement of the two elements is usually different. So when one of the elements is in position stop, the other element stops its movement as well. In order to finish the movement tipping or lifting completely, the operator must intervene on the system. function of the cylinder which has not finished its stroke, the operator must change the position of the solenoid valve and choose either the “tipping” position in which only the cylinder dumping is supplied with hydraulic fluid to allow only the movements of a handling device, for example a bucket, or a so-called position of "claw manipulation" in which only the claw cylinder is supplied with liquid hydraulic to allow only the movements of said claw. This man- The rotation takes place after an interruption of the synchronized movement of the two elements and wastes time. These manipulations are intended to be repeated many times in the context of handling work. The repetition of these man- pulses represent a loss of time that occurs on each of the work cycles causing fatigue for the operator and slowing down the rate of tipping or lifting work. The invention thus aims to improve synchronization control systems by allowing tipping or lifting movements to be carried out completely without interruption and without operator intervention. Summary of the invention Thus, the invention relates to a system for controlling the synchronization of the movements of two elements, for example a claw and a handling member such as a bucket, the position of the first element being controlled by a first control system, the position of the second element being controlled by a second control system, the synchronization control system comprising a system for synchronizing said first and second control systems adapted to modify the positions of the two elements concomitantly by means of a hydraulic circuit in series, characterized in that the elements have different position amplitudes and in that it comprises a movement continuation system adapted to allow that, when one of the elements reaches a stop position, the other element continues its movement to a stop position. Position amplitude refers to the number of degrees between the two stop positions that an element can assume. Thus, the position amplitude is a property of each element, for example, a claw and a handling device such as a bucket. Stop position refers to the fully extended or fully retracted position of a control means. Each cylinder can therefore have two stop positions: either the cylinder is at the end of a first stroke, i.e., in the most extended position possible, or the cylinder is at the end of a second stroke in a direction opposite to the first, i.e., in the most retracted position possible. Thanks to these arrangements, at least one of the movements can be accomplished from one stop position to the other stop position of the two elements continuously, i.e., without interruption and without operator intervention during the movement. Depending on different aspects, it is possible to provide one and / or the other of the characteristics below taken alone or in combination. According to one embodiment, the first control system comprises a so-called "tipping" hydraulic cylinder comprising two chambers connected to a hydraulic circuit, and the second control system comprises a so-called "claw" hydraulic cylinder, the two cylinders being mounted in series on a hydraulic supply circuit via a selection solenoid valve in the so-called "synchronization" position, thus a communication of hydraulic liquid is created between the so-called "opening" chamber “claw” chamber of the claw cylinder, and the so-called “lifting” chamber of the tipping cylinder, and in which the exhaust system is adapted to allow said communication of hydraulic fluid to continue when one of the two cylinders is in the stop position. Thus, it is possible to have enough power to handle a heavy load from standard elements available in the industry whose size, weight and cost are compatible with the use for which this system is intended. According to one embodiment, the selection solenoid valve allows two other connection positions, a so-called "tipping" position in which only the tipping cylinder is supplied with hydraulic fluid to authorize only the movements of the handling member and a so-called "claw movement" position in which only the claw cylinder is supplied with hydraulic fluid to authorize only the movements of said claw. Thus, if necessary, the operator can operate only one of the control means. In many cases, it is necessary to use only the first element or only the second element. For example, one may want to tighten hay bales using a claw without steering a bucket or, on the contrary, steer a stack of hay bales without changing the tightening of a claw, for example. Several embodiments are possible for the subsystem allowing the communication of hydraulic fluid to continue when one of the two cylinders is in the stop position. According to one embodiment, the subsystem comprises four pressure limiters activated only in the synchronization position, the pressure limiters being mounted in parallel two by two in opposite directions between an upstream connection of the selection solenoid valve and a downstream connection of the selection solenoid valve so that when a hydraulic claw cylinder is at the stop, the supply of the other hydraulic cylinder continues via one of the four pressure limiters. Thus, the subsystem is simple, inexpensive and easily integrated into a system for controlling the synchronization of the movements of two elements of the prior art. According to one embodiment, the pressure limiters are connected to connections integrated into the selection solenoid valve, said connections being disconnected from the hydraulic circuit when the selection solenoid valve is in the dump or claw movement position, allowing activation of said pressure limiters only in the synchronization position. Thus, a single simple modification of the prior art solenoid valve makes it possible to implement the invention. According to one embodiment, the control system comprises four isolation solenoid valves, each isolation solenoid valve being in the supply position only in the synchronization position, mounted in series with each of the pressure limiters. According to one embodiment, the hydraulic fluid communication between the so-called "claw opening" chamber of the claw cylinder and the so-called "lifting" chamber of the tipping cylinder comprises a connection to a hydraulic fluid communication bridge connected to an outer end of the hydraulic loop, said communication bridge comprising a restriction, said restriction being capable of allowing the flow of hydraulic fluid to pass through the communication bridge when a hydraulic cylinder is in the stop position. According to one embodiment, four pressure sensors detect the pressure in each of the four chambers of the double-acting hydraulic cylinders, the pressure sensors control the connection configurations of the solenoid valve so that, when the hydraulic pressure exceeds a threshold corresponding to a stop position, the pressure sensors trigger the passage of the solenoid valve from the synchronization position to the position where the second cylinder is supplied with hydraulic pressure. According to one embodiment, four position sensors communicate the detection of a stop position of a first hydraulic cylinder to a control unit capable of modifying the power supply to the solenoid valve in order to trigger the change in configuration of the solenoid valve to the position where only the second hydraulic cylinder is supplied with hydraulic pressure. According to one embodiment, the subsystem comprises four hydraulic valves, the opening of which is activated by one of the two elements reaching a stop position, each hydraulic valve being capable of short-circuiting the hydraulic supply of a hydraulic cylinder which has reached a stop position. According to one embodiment, the chambers of the double-acting hydraulic cylinders comprise an additional orifice, each of said additional orifices passing from one chamber to the other when the hydraulic cylinder is in a stop position, said orifice being connected both to the part of the hydraulic circuit which allows the hydraulic fluid to circulate in the chamber of the hydraulic cylinder which has reached the stop position via a one-way valve and to the part of the circuit which supplies the other chamber of the same hydraulic cylinder. Brief description of the drawings Embodiments of the invention will be described below with reference to the drawings, briefly described below: [Fig.1] represents a control system according to an embodiment of the invention comprising 4 pressure limiters. [Fig.2] represents a control system according to an embodiment of the invention comprising 4 solenoid valves. [Fig.3] shows a control system according to an embodiment of the invention comprising a restriction. [Fig.4] shows a control system according to one embodiment of the invention comprising four pressure sensors. [Fig.5] shows a control system according to one embodiment of the invention comprising four decompression valves. [Fig.6] represents a control system according to an embodiment of the invention comprising four decompressions on jacks. [Fig.7] represents a part of the control system according to an embodiment of the invention comprising 4 orifices per cylinder with the claw cylinder in a first stop position. [Fig.8] shows a part of a control system according to an embodiment of the invention with the claw cylinder in a second stop position. [Fig.9] shows part of a control system according to an embodiment of the invention in which two two-position solenoid valves replace a three-position selector solenoid valve. In the drawings, like references designate identical or similar objects. DETAILED DESCRIPTION In the figures, the reference T denotes a tractor, for example an agricultural tractor, equipped with a front loader C usually comprising an articulated stretcher B provided at its front end with a tool-carrying frame CP. The loader comprises a pair of lifting cylinders VL, said lifting cylinders VL allow the stretcher B to pivot around its articulation axis X, relative to the chassis of the agricultural tractor T, so as to cause the lifting or lowering relative to the chassis of an implement O carried by the frame CP. The tool O comprises a handling member, a bucket 2, an example of what will generally be considered the “first element” in the remainder of the description, associated with a claw 3, an example of what will generally be considered the “second element” in the remainder of the description. According to other variant embodiments not shown in the figures, the tool O can also be a silage unloading tool in which the handling member is a vertical flat frame provided at its base with a series of teeth or a manure fork in which the handling member is also a bucket but also very slightly concave. equipped with teeth. In the remainder of the description and for the purposes of simplification, it has been considered that the handling member is a bucket 2. Thus, in the figures, the handling member is a bucket 2, that is to say a hollow tool or bucket. The loader C also includes a pair of dumping cylinders 1 positioned symmetrically along the vertical plane of symmetry of the tractor, double-acting, allowing the tool O to pivot relative to the stretcher B around an axis X1. Cylinders 1 constitute means for controlling the orientation of the dump body 2. Each tipping cylinder | comprises a tipping piston 10 secured to the tool-carrying frame CP and a tipping cylinder 11 secured to the stretcher B. The dumping piston 10 and the dumping cylinder 11 form a first chamber 110 in which the rod of the dumping piston 10 passes, called the “lifting chamber” 110, and a second chamber 111 called the “dump chamber” 111 opposite the first lifting chamber 110 formed by the walls of the dumping cylinder 11 and the head of the dumping piston 10. The claw 3 is equipped with a pair of cylinders 4, hereinafter referred to as claw cylinders 4. The claw cylinders 4 constitute means for controlling the opening and closing of the claw 3. Each double-acting claw cylinder 4 comprises a claw piston 40 secured to the claw 3 and a claw cylinder 41 secured to the upper part of the bucket 2. Each claw cylinder 4 further has a first chamber 410 called the “claw opening chamber” 410 in which the rod of the claw piston 40 passes and a second chamber 411, on the opposite side called the “claw closing chamber” 411. Usually, the T tractor is equipped with a high pressure HP hydraulic source (pressure of the order of 1.5.107 to 2.107 Pa). A line 8 corresponds to the line which brings high pressure hydraulic fluid from the hydraulic source to the rest of the hydraulic circuit, and a line 9 corresponds to the line which allows the hydraulic fluid to return to the reservoir (return noted “BP” for “low pressure”). The conduits 8 and 9 are connected to a control distributor 5 with three positions 50, 51, 52. The control distributor 5 is connected via two connections 81 and 82 to a selection solenoid valve 6 with three positions 61, 62, and 63. When position 50 of the control valve is selected, as shown [Fig.1], the so-called "neutral" position, a loop connects conduit 8 to conduit 9, thus isolating the rest of the connections and conduits from any hydraulic pressure. Thus, the selection solenoid valve 6 does not receive any hydraulic command. When position 52 of the control valve is selected, the hy- The hydraulic power from conduit 8 is sent to connection 82 and connection 81 is connected to conduit 9. When position 51 of the control valve is selected, the hydraulic pressure from conduit 8 is sent into connection 81 and connection 82 is connected to conduit 9. In the remainder of the description, it will be assumed that position 51 of the control distributor 50 is selected. Each of the three positions 61, 62, and 63 of the selection solenoid valve 6 comprises a connection to connection 81, respectively 618, 628 and 638, and a connection to connection 82, respectively 619, 629 and 639. The selection solenoid valve 6 is connected to a movement tracking subsystem 1000, shown in [Fig. 1], adapted to allow the movement of one element to continue when the selection solenoid valve 6 is in a synchronization position 63 and the other element is in the stop position. The selection solenoid valve 6 is controlled by a command. Six connections between the selector solenoid valve 6 and the motion tracking subsystem 1000 are referenced 93, 94, 95, 96, 97 and 98. When the selection solenoid valve 6 is in position 62, only the connections 97 and 94 are connected to the hydraulic supply delivered via the connections 628 and 629. Thus, only the cylinders 4 of the claw 3 are actuated. In this configuration, the high-pressure oil enters the claw opening chamber 410, and the movement of the piston of the claw cylinder forces the oil from the claw closing chamber 411 towards the reservoir (LP side). Similarly, when the selection solenoid valve 6 is in position 61, only the connections 96 and 93 are connected to the hydraulic supply delivered via the connections 618 and 619. Thus, only the cylinders 1 of the bucket 2 are actuated. In this configuration, the high-pressure oil enters the dump chamber 111, and the movement of the piston of the bucket cylinder forces the oil from the lifting chamber 110 towards the reservoir (LP side). In the remainder of the description, it will be assumed that position 63 of the selection solenoid valve 6 is selected, unless otherwise indicated. This position 63 makes it possible to actuate both the bucket cylinders and the claw cylinders. The connections 96 and 94 are connected to the hydraulic supply delivered via the connections 618 and 619. The connections 93 and 97 are connected to each other. The motion tracking subsystem 1000 is connected to the dump cylinders 1 and to the claw cylinders 4 by four connections referenced 83, 84, 85 and 86 which respectively supply the dump chamber 111, the lifting chamber 110, the claw closing chamber 411 and the claw opening chamber 410. In this configuration, the high-pressure oil enters the dump chamber 111, and the movement of the piston of the dump cylinder forces the oil from the lifting chamber 110 towards the claw opening chamber 410 via the connections 93 and 97. The movement of the piston of the claw cylinder forces the oil from the claw closing chamber 411 towards the reservoir (LP side) through the connections 85, 639, 82 and 9. Thus, in this configuration, the dump is lowered and the claw is opened simultaneously. In a first embodiment shown in [Fig. 1], a motion tracking subsystem 1000 is connected between connections 93, 94, 95, 96, 97 and 98 on one side and connections 83, 84, 85 and 86 on the other. The motion tracking subsystem 1000 comprises 4 unidirectional pressure limiters 1010, 1020, 1030 and 1040 mounted in two parallel groups two by two in opposite direction comprising two connection sides, the limiters 1010 and 1020 forming a first group of pressure limiters connected between connection 93 and connection 84 on one side and connection 95 on the other side. In the selection solenoid valve, connection 95 is connected to connection 638 (“HP” side in this configuration). The pressure limiters 1030 and 1040 form a second group of pressure limiters connected between connection 93 and connection 84 on one side of said second group and connection 98 on the other side. In the selection solenoid valve, connection 98 is connected to connection 639 (“LP” side in this configuration). The one-way pressure relief valves 1010, 1020, 1030 and 1040 are connected to the connections 95 and 98 in the selection solenoid valve 6, so that they can only act when the selection solenoid valve 6 is in the synchronization position 63. In fact, as can be seen in [Fig. 1], in positions 61 and 62, connections 95 and 98 are disconnected from the hydraulic circuit. In positions 61 and 62, their effect on the hydraulic circuit could generate short circuits, preventing the normal operation of the control system, i.e. the movement of only one of the two elements: bucket 2 or claw 3. When the hydraulic pressure is applied via the connection or the conduit 8, the system being in the configuration corresponding to the two hypotheses chosen for the remainder of the description, when none of the cylinders is in the stop position, said pressure is transmitted via the connections 638 and 96 to the dumping chamber 111. This pressure actuates the dumping piston 10 which deploys in a linear movement leaving the dumping cylinder 11. This movement also pressurizes the hydraulic contents of the lifting chamber 110. As in position 63, the connection 84 is connected to the connection 93 which is connected to the connection 97, as connection 97 is connected to connection 86, hydraulic pressure from lift chamber 110 is applied to claw opening chamber 410. Thus, the claw piston 40 retracts in a linear motion entering the claw cylinder 41. Connection 85, via connection 94 and connection 639 allows the hydraulic fluid from the claw closing chamber 411 to drain into conduit or connection 9. Thus the opening of the claw and the tipping are done simultaneously. In this movement, and in the case where the claw reaches the stop before the bucket reaches the stop, the pressure in the claw opening chamber 410 increases, which increases the pressure at the connections 86, 97 and at the inlet of the pressure limiter 1010 and at the connection 84. As the dumping chamber 111 is under pressure, the hydraulic pressure applied at the connection 84 cannot escape into the lifting chamber 110. It is therefore evacuated via a hydraulic flow through the pressure limiter 1010 and reinforces the pressure already applied at the connection 96 via the connection 95 in the dumping chamber 111. In the same synchronized movement of opening of the bucket, and in the opposite case to the previous one, that is to say in the case where the bucket 2 reaches the stop before the arrival at the stop of the claw 3, the pressure in the dumping chamber 111 increases as well as the pressure at the connections 83, 96 and 95 until the pressure limiter 1020 allows a hydraulic flow to pass through the connection 95 in the direction of the connection 93. Indeed, as the connection 84 supplies the lifting chamber 110 and the dumping chamber 111 is subjected to a high hydraulic pressure, the bucket remains at the stop. The hydraulic pressure at the outlet of the pressure limiter 1020 is then applied at the connection level 93, 97 and 86. The connection 86 being located at the supply level of the claw opening chamber 410, the claw opening chamber 410 continues to be supplied with hydraulic pressure when the bucket 2 is in the stop position.With the claw closing chamber 411 connected to the conduit or connection 9 via the connections 85, 94 and 639, emptying of the claw closing chamber 411 continues when the bucket 2 is in the stop position. Thus, thanks to this subsystem, the tipping or claw opening movement in progress continues even when one of the elements has reached the stop without any intervention on the system. The operation is identical with simply a reversal of the hydraulic flow and the implementation of limiters 1030 and 1040 instead of limiters 1010 and 1020 in the case of the synchronized movement of lifting and closing of the claw. The operation in position 52 of the control distributor 5 is deduced simply from the operation in position 51, because it is a reversal of the direction of the hydraulic flow in the rest of the hydraulic circuit of the system which is identical, mutatis mutandis. In a second embodiment, illustrated [Fig.2], the pressure limiters 1010, 1020, 1030, 1040 are not connected to dedicated connections of the selection solenoid valve 6, unlike the embodiment above, but directly to the connections 96 and 94 (as well as the return always connected to the connection 93). Isolation solenoid valves 1110, 1220, 1330, 1440 are mounted respectively in series upstream of the pressure limiters 1010 and 1030, and downstream of the pressure limiters 1020 and 1040. The isolation solenoid valves 1110, 1220, 1330, 1440 are electrically connected with the control 64 of the selection solenoid valve 6 so that the isolation solenoid valves 1110, 1220, 1330, 1440 only allow the hydraulic flow to pass when the position 63 of the selection solenoid valve 6 is activated. This prevents the pressure limiters 1010, 1020, 1030, 1040 from being connected to the hydraulic circuit in positions 61 and 62 of the selection solenoid valve 6. In fact, in positions 61 and 62, their effect on the hydraulic circuit could generate short circuits, preventing the normal operation of the control system, i.e. the movement of only one of the two elements: the bucket 2 or the claw 3. When position 63 is selected, the motion tracking subsystem 1000 operates exactly as in the first embodiment illustrated by [Fig. 1], mutatis mutandis. In a third illustrated embodiment [Fig. 3], a motion tracking subsystem 2000 is integrated at position 63. In the remainder of the description, it will be assumed that position 63 of the selection solenoid valve 6 is selected, unless otherwise indicated. A restriction 2001 is positioned on the hydraulic conduit between connection 638 and connection 2002 of the selection solenoid valve 6 when it is in position 63 in order to connect the conduit 9 via connection 84 to the lifting chamber 110. When neither the bucket 2 nor the claw 3 is in the stop position, the hydraulic pressure arrives in the dumping chamber 111 via the connections 639, 2004 and 83, the pressure is transmitted to the contents of the lifting chamber 110. The hydraulic flow leaving the lifting chamber 110 then circulates essentially through the connection 2005 and feeds the pressure in the claw opening chamber 410. The claw closing chamber 411 empties its hydraulic contents into the conduit 9 via the connections 85, 2003 and 638. When bucket 2 is not in the stop position and claw 3 is in the stop, the hydraulic flow can no longer pass via the connection 2005 so that the flow passes through the restriction 2001 in order to be evacuated via the connection 638 into the conduit 9. The restriction 2001 thus makes it possible to continue to operate the bucket 2 while the claw 3 is in the stop position. When the direction of hydraulic flow is reversed, hydraulic flow passes via connections 638 and 2003 into the claw closing chamber 411. Pressure is then transferred to the contents of the claw opening chamber 410 which passes via connections 2005 and 2002 into the lifting chamber 110. The dump chamber 111 empties via connections 2004 and 639 into conduit 9. In this reversed direction of hydraulic flow, when the claw 3 is in the stop position and the bucket 2 is not in the stop position, the flow can no longer pass via the connection 2003. The flow then feeds the lifting chamber 110 via the restriction 2001 and the connection 2002. The restriction 2001 thus allows the bucket 2 to continue to be operated while the claw 3 is in the stop position. In a fourth illustrated embodiment [Fig. 4], a motion tracking subsystem 3000 comprises four pressure sensors 3010, 3020, 3030, 3040 which sense the pressure at the conduits connected respectively to the connections 83, 84, 86 and 85. As long as neither of the two bucket elements 2 and claw 3 is in the stop position, the hydraulic circuit operates in the same way as that described in [Fig.1], mutatis mutandis. When one of the four pressure sensors 3010, 3020, 3030, 3040 detects a hydraulic pressure above a certain threshold greater than the nominal hydraulic pressure, the sensor detects the crossing of the threshold and then triggers a change in position of the selection solenoid valve 6. The change in position of the selection solenoid valve 6 is carried out from position 63 to one of the positions 61, 62 which only allows the movement of the element 2 or 3 which is not in the stop position. A variant of the motion tracking subsystem 3000 not illustrated comprises a control unit which receives the detection signals emitted by four position sensors capable of detecting an end-of-travel position of one of the cylinders, and of generating in the case of a detected end-of-travel, either directly or through a control unit, a command sent to the selection solenoid valve 6 to switch from position 63 to one of positions 61, 62 which only allows the movement of the element 2 or 4 which is not detected in the stop position. In a fifth illustrated embodiment [Fig. 5], a motion tracking subsystem 4000 comprises four hydraulic valves 4010, 4020, 4030 and 4040 connected respectively to four position detectors which are connected respectively between connections 83 and 84 for the first two opposite hydraulic valves 4010 and 4020, and between connections 85 and 86 for the other two opposite hydraulic valves 4030 and 4040. The four hydraulic valves 4010, 4020, 4030 and 4040 are configured to be in the open position, i.e. do not allow hydraulic fluid to pass through, as long as no stop position is reached. Each of the hydraulic valves 4010, 4020, 4030 or 4040 is configured to move to the closed position when the element to which it is connected is in one of the two stop positions. The hydraulic valve 4010 moves to the closed position when the bucket cylinder 2 reaches the stop position at the end of a lifting movement. The hydraulic valve 4020 moves to the closed position when the bucket cylinder 2 reaches the stop position at the end of a dumping movement. The hydraulic valve 4030 moves to the closed position when the claw cylinder 3 reaches the stop position at the end of a claw closing movement 3. The hydraulic valve 4040 moves to the closed position when the claw cylinder 3 reaches the stop position at the end of a claw opening movement 3. These hydraulic valves are for example mechanically controlled by contact with mechanical parts of the claw or of the tipping assembly. As long as neither of the two elements, bucket 2 and claw 3, is in the stop position, the hydraulic circuit operates in the same way as that described in [Fig.1], mutatis mutandis. When a stop position is reached by a first element, one of the two solenoid valves allowing the hydraulic pressure supply to the cylinder of the element in stop position to be short-circuited allows the movement of the other element to continue until it reaches the stop position. When the two elements, bucket 2 and claw 3, are in the stop position, all the cylinders of the two elements 1 and 4 are short-circuited. The operator therefore does not even need to position the control distributor 5 in position 50 at the end of the two synchronized movements of the two elements, i.e. here bucket 2 and claw 3. The subsystem 4000 short-circuits the supply to the chambers, so that there is no longer any pressure exerted in any of the chambers when the two elements are in the stop position. There is thus no unnecessary pressure applied to the cylinders, which avoids unnecessary material strain that can prematurely age the control system. In a sixth illustrated embodiment [Fig. 6], a subsystem 5000 is implemented at the level of the supply of the chambers with hydraulic pressure. Each of the main orifices a, b, c and d, of the chambers respectively 111, 110, 410, 411 of the tipping cylinder 1 and of the claw cylinder 4 has a secondary orifice a', b°, c', d' slightly upstream of the main ports a, b, c and d. the ports a', b', c' and d' are connected respectively to the connections 83, 84, 85 and 86 via one-way valves 5010, 5020, 5030 and 5040, respectively. The positioning of the secondary ports c', d' is such that, when the claw 3 is in the stop position, as shown in figures 7 or 8, the secondary port c' and d', normally communicating with the chamber whose volume can no longer decrease due to the stop position of one of the elements, then communicates with the opposite chamber of the same cylinder. Thus a short circuit is created at the level of the opposite chamber thus allowing the hydraulic fluid to continue to circulate in the other chambers of the other cylinder. A similar operation is provided with the ports a' and b' when the bucket is in the stop position.The 5000 subsystem bypasses the power supply to the chambers, so that there is no pressure exerted in either chamber when the two elements are in abutment. This means that there is no unnecessary pressure applied to the cylinders, which avoids unnecessary material fatigue that can prematurely age the control system. The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art. In particular, the single three-position solenoid valve 6 can be replaced by two separate selectors each having two positions, as shown [Fig.9]. This variant is compatible with the other embodiments described above, for example that of [Fig.5]. List of reference signs T: Agricultural tractor C: front loader B: articulated stretcher CP: tool frame VL: lifting jacks X: axis of articulation of stretcher B O: tool 2: dumpster 3: claw X1: pivot axis of tool O relative to stretcher B 1: tipping cylinder 10: dump piston 11: dump cylinder 110: lifting chamber 111: dumping room 4: claw cylinders 40: claw piston 41: claw cylinder 410: claw opening chamber 3 411: claw closing chamber 3 8: high pressure conduit 9: low pressure conduit 5: Control distributor 50, 51, 52: positions of control valve 5 6: selection solenoid valve 81, 82: connections connecting the control distributor 5 to the selection solenoid valve 61, 62, 63: positions of the selection solenoid valve 6 618, 628, 638: connections connected to connection 81 depending respectively on position 61, 62, 63 of the selection solenoid valve 6 619, 629, 639: connections connected to connection 82 depending respectively on position 61, 62, 63 of the selection solenoid valve 6 1000, 2000, 3000, 4000: subsystem allowing the movement of an element 2 or 3 to continue when the selection solenoid valve 6 is in a synchronization position 63 and the other element 3 or 2 is in the stop position. 64: control of the selection solenoid valve 6 93, 94, 95, 96, 97, 98: connections between the selection solenoid valve 6 and the subsystem 1000 83, 84, 85 and 86: connections between subsystem 1000 and tipping cylinders 1 and to claw cylinders 4 1010, 1020, 1030 and 1040: one-way pressure relief valves 1110, 1220, 1330, 1440: isolation solenoid valves 2001: restriction 2003: connection downstream of the 2001 restriction 2004: connection 2003 which connects the claw closing chamber 411 to conduit 8 2005: upstream connection of restriction 2001 with claw opening chamber 410 3010, 3020, 3030, 3040: pressure sensors 4010, 4020, 4030 and 4040: hydraulic valves a, b, c and d: main orifices of chambers 110, 111, 410, 411 of the two tipping cylinders 1 a', b', c' and d': secondary orifices of the chambers 110, 111, 410, 411 of the two tipping cylinders 1

Claims

Claims

1. System for controlling the synchronization of the movements of two elements, for example a claw (3) and a handling member (2) such than a bucket, the position of the first element (2) being controlled by a first control system (1), the position of the second element (3) being controlled by a second control system (4), the synchronization control system comprising a system of synchronization (6) of said first and second control systems (1, 4) adapted to modify the positions of the two elements (2, 3) conco- partly by means of a series hydraulic circuit, characterized in that that the elements have different position amplitudes and that it includes a motion tracking system adapted to allow that, when one of the elements reaches a stop position, the other element continues its movement to a stop position.

2. A control system according to claim 1, wherein the first control system (1) comprises a hydraulic cylinder called “dump” comprising two chambers connected to a hy- hydraulic, and the second control system (4) comprises a hy- hydraulics called “claw”, the two jacks (1) and (4) being mounted in series on a hydraulic supply circuit via a solenoid valve selection (6) in position (63) called “synchronization”, thus a com- hydraulic fluid communication is created between the chamber (410) called “claw opening” of the claw cylinder (4), and the chamber (110) called "lifting" of the dump cylinder (1), and in which the system exhaust is adapted to allow said communication of hydraulic fluid to continue when one of the two cylinders is in stop position.

3. A control system according to claim 2, wherein the selection solenoid valve (6) allows two other positions of connection, a position (61) called "tipping" in which only the dump cylinder (1) is supplied with hydraulic fluid to allow only the movements of the handling device (2) and a position (62) called “claw movement” in which only the cylinder claw (4) is supplied with hydraulic fluid to allow only the movements of said claw (3).

4. Control system according to one of claims 2 or 3, in which subsystem (1000) comprises four pressure limiters (1010, 1020, 1030, 1040) activated only in sync position- nization, the pressure limiters (1010, 1020, 1030, 1040) being mounted in parallel two by two in opposite directions between a connection upstream (638, 639) of the selection solenoid valve (6) and a connection downstream of the selection solenoid valve (6) so that when a hy- hydraulic claw is at the stop, the supply of the other hy- draulic continues via one of the four pressure limiters (1010, 1020, 1030, 1040).

5. A control system according to claim 3 and 4, wherein the pressure limiters (1010, 1020, 1030, 1040) are connected to connections integrated into the selection solenoid valve (6), said connections being disconnected from the hydraulic circuit when the selection solenoid valve (6) is in the dump position (61) or claw movement (62), allowing the activation of said limiters of pressure (1010, 1020, 1030, 1040) only in sync position- nization.

6. A control system according to claim 4, comprising four elec- isolation valves (1110, 1220, 1330, 1440), each solenoid valve isolation being in the supply position only in the supply position synchronization (63), mounted in series with each of the limiters pressure (1010, 1020, 1030, 1040).

7. A control system according to claim 2 or 3, wherein the communication of hydraulic fluid between the chamber (410) called “claw opening” of the claw cylinder (4) and the chamber (110) called “of lifting” of the dump cylinder (1) includes a connection to a bridge hydraulic fluid communication connected to one end ex- inside the hydraulic loop, said communication bridge comprising a restriction, said restriction being capable of allowing the flow to pass of hydraulic fluid in the communication bridge when a jack hydraulic is in the stop position.

8. A control system according to claim 3, wherein four pressure sensors (3010, 3020, 3030, 3040) detect the pressure in each of the four chambers (110,111, 410, 411) of the hy- double-acting hydraulics (1,4), pressure sensors (3010, 3020, 3030, 3040) control the connection configurations of the solenoid valve (6) so that when the hydraulic pressure exceeds a threshold corresponding to a stop position, the pressure sensors (3010, 3020, 3030, 3040) trigger the passage of the solenoid valve of the synchronization position (63) to the position where the second cylinder is supplied with hydraulic pressure.

9. A control system according to claim 8, wherein four position sensors communicate the detection of a stop position from a first hydraulic cylinder to a control unit capable of modify the power supply to the solenoid valve (6) in order to trigger the change of configuration of the solenoid valve (6) to the position where only the second hydraulic cylinder is supplied with hydraulic pressure.

10. Control system according to one of claims 2 or 3, in which subsystem (4000) comprises four hydraulic valves (4010, 4020, 4030, 4040) whose opening is activated by an arrival in stop of one of the two elements (2, 3), each hydraulic valve being capable of short-circuiting the hydraulic supply of a hydraulic cylinder arrival at a stop position.

11. Control system according to one of claims 2 or 3, in which the chambers (110,111, 410, 411) of the hydraulic cylinders double effect (1,4) include an additional orifice (a', b°, c', d'), each of said additional orifices (a', b°, c', d') passing from a chamber to the other when the hydraulic cylinder is in a position of stop, said orifice being connected both to the part of the hy- circuit hydraulics which allows the hydraulic fluid to circulate in the hydraulic cylinder chamber reached the stop position via a valve unidirectional and to the part of the circuit which feeds the other chamber of the same hydraulic cylinder.